Spin-on filter assemblies include two parts—a filter head with a threaded spud and a removable and replaceable filter cartridge. The filter head is typically permanently mounted to equipment, such as an engine, hydraulics, or a generator. The filter head has inlet channels for conveying fluid to be filtered to the filter cartridge, and outlet channels for conveying fluid that has been filtered by the cartridge for use by the equipment. The filter cartridge will typically include an outer can or housing holding a filter element of filter media therewithin. The filter cartridge is typically useable over some limited duration due to the limited life of the filter media within. The filter cartridge is removed from the filter head and disposed of and is then replaced with a new filter cartridge. The filter cartridge and filter head are removably connected to each other, typically through a threaded connection. The spud on the filter head will typically have threads, while the filter cartridge will have a threaded aperture to fit on the threaded spud. The threaded connection between the filter cartridge and filter head can sometimes present a leak path for unfiltered fluids. That is, sometimes fluid that has not been filtered can travel along the threads and reach the clean side of the filter without first passing through the filter media. This leakage can lead to particulate material traveling to downstream equipment, which can present problems. Improvements are desirable.